Which gland consists of a coiled gland with a duct that connects to the surface of the skin?

The correct answer is the eccrine gland, which is indeed a coiled gland that connects to the surface of the skin through a duct. Eccrine glands are a type of sweat gland that plays a crucial role in thermoregulation and maintaining the body's temperature by producing a watery secretion that evaporates and cools the skin. These glands are distributed throughout the body, particularly on the palms, soles, and forehead.

The coiled structure of the eccrine gland allows for the efficient production and storage of sweat, with the duct facilitating its release directly onto the skin's surface. This design is essential for the gland's function in perspiration and sweat management.

Other glands mentioned serve different functions. Apocrine glands, for instance, also produce sweat but release it into hair follicles rather than directly onto the skin surface. Sebaceous glands secrete sebum into hair follicles to lubricate the skin and hair, and the pineal gland is an endocrine gland located in the brain that regulates sleep patterns through the secretion of melatonin. Thus, the unique structure and function of eccrine glands make them the correct answer to the question.